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SSS Subfootprint Variability in the SPURS-1 and SPURS-2 Regions
[28-Aug-18] Bingham, F.
Presented at the 2018 Ocean Salinity Science Team and Salinity Continuity Processing Meeting
Using the SPURS-1 and SPURS-2 datasets, I calculated the subfootprint variability (SFV) of sea surface salinity (SSS). The SFV was defined as the weighted standard deviation of SSS within a 50 km distance of the central mooring for each field campaign. Data for SPURS-1 included drifters, shipboard TSGs, wavegliders, etc. For SPURS-2 the calculation was only done using waveglider data. Separate calculations were done for each field campaign using weekly mooring records, plus a high resolution ROMS model run.
For SPURS-1, SFV was generally less than 0.1. Sigma_95, defined as the value which exceeds 95% of SFV values, was 0.11. For SPURS-2, SFV was much higher, with a sigma_95 value of 0.29. Variability of SFV at SPURS-2 was also much more seasonal than SPURS-1. Low values of SFV, similar to those found at the SPURS-1 site, were persistent during the November-June 2016/2017 time period. Outside of that period, SFV was variable and much higher.
The higher values of SFV during SPURS-2 were a result of low SSS outliers measured by the in situ observations, presumably associated with rain events, and also the eastern Pacific fresh pool which appears in the region during the fall and winter. This study highlights the variable nature of SFV, its seasonality in certain parts of the ocean, its association with advective features, and its size relative to instrumental and other errors in the satellite retrieval of SSS.

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